[al Furqaan]

Disagree with the OP's math of 6 wins minimum, unless he's assuming that BD will have a bad net run rate - which is entirely plausible. Here's a potential scenario of final standings before the semifinals:

1) England 8-1 (only loss to India)
2) India 7-2 (losses to Sri Lanka and Australia)
3) Australia 6-3 (losses to England, Pakistan, South Africa)
4) Bangladesh 5-4 (losses to England, India, Australia, New Zealand)

5) New Zealand 5-4 (losses to England, India, Australia, South Africa)
6) South Africa 4-5 (losses to England, Bangladesh, India, Pakistan, Afghanistan)
7) Pakistan 4-5 (losses to England, India, Bangladesh, New Zealand, West Indies)
8) Afghanistan 3-6 (wins vs Sri Lanka, West Indies, South Africa)
9) West Indies 2-7 (wins vs Pakistan, Sri Lanka)
10) Sri Lanka 1-8 (only win vs India)

The only upsets in this setting are:

SL beating India (happened in 2017 CT)
PAK beating Australia
BD beating South Africa
AFG beating South Africa
WI beating Pakistan

So very few "shock results". Remember that SA asides from choking, are extremely weak against spin, so its conceivable BD and AFG could trouble them.

We see BD and NZ it will come down to NRR, and of course BD is 95% likely to lose any NRR battle.

But the point is, that 6 wins will be safe, but I believe one semifinalist will have just 5 wins.

It should be noted that there are several permutations that will result in such standings, the one I gave is just one [likely] one.